Cadillac Seville / Cadillac Eldorado Forum Discussion, 99 seville 100% tranny life since day one in Past Cadillac Vehicle Discussion; Originally Posted by 1toycad
Jim, I agree that it is cheap insurance. In that case, shouldn't we change it at ...

Re: 99 seville 100% tranny life since day one

The transmission fluid in modern cars is easily good for the life of the car in normal driving. Running it to 100K is very "safe" and will cause no harm to the tranny. Tranny fluid isn't like engine oil. It's not exposed to blow by and by products of combustion. It doesn't see copius amounts of water from blowby on coldstarts. There's not much to deplete the lubricating characteristics of the tranny oil and the antiwear and special friction modifier packages are very robust and stable. The temperature of the transmission fluid is pretty carefully controlled in the cooling development for the car. About the only thing that will shorten the tranny fluid's life is excessive heat and excessive heat for long periods of time. Since the modern tranny fluid has a high synthetic content it is pretty stable even at temperatures approaching 300 degrees. So the things that govern an oil change in an engine don't apply to the transmission at all.

The transmission fluid life "counter" in the display uses the tranny temperature as a means of judging the transmission fluid's life. As long as nothing is done that the algorithm sees to shorten the life of the fluid it will stay at 100% virtually forever. If you start towing trailers or running extended heavy load operation you will see the tranny fluid life decrement fairly rapidly. If it is "stuck" on 100% then that means that the operating parameters that the PCM sees for the trans fluid have all remained well within the guidelines for life time use of the fluid. The transmission oil life monitor does not operate the same way the engine oil life monitor operates so you will typically see it stay at 100% in most cases.

Re: 99 seville 100% tranny life since day one

I have a 1997 sts & i changed my tranny fluid at 1oooo mi as said in service manuel.I changed by a transtech sysyem,it,s the only system that gets 1oo%of the old fluid out including clutch drums,shift controller & torque converter+ new filters for $140.00.I am from the old school,i dont trust life of car stuff, fluid wears out, i would rather ride then walk. DAVE!

Re: 99 seville 100% tranny life since day one

Originally Posted by davestpierre

I have a 1997 sts & i changed my tranny fluid at 1oooo mi as said in service manuel.I changed by a transtech sysyem,it,s the only system that gets 1oo%of the old fluid out including clutch drums,shift controller & torque converter+ new filters for $140.00.I am from the old school,i dont trust life of car stuff, fluid wears out, i would rather ride then walk. DAVE!

Did "you" change it or did you have it changed at a shop? Not likely that you changed the filter in a 4T80E as you have to drop the transmission to get to the filter that's located in the side cover. There are two screens on the oil pickups in the bottom pan but they are not generally replaced - just cleaned of any debris. The 4T80E operates as a dry sump unit that has scavenge pumps that pick oil up from the bottom pan through the two pickups and deliver it to the side cover where it is stored. From there, the main line pressure pump picks up the oil thru the actual filter. The filter on a 4T80E is only replaced in the event of a trans failure or rebuild for some reason.

Search our archives using the search feature and type in "trans flush", "tranny flush" and/or "transmission flush" for some interesting reading. Not the most desireable thing to do given the risk of contamination from the flushing equipment.

Simply dropping the bottom pan and also draining the fluid from the side cover via the hidden drain plug under the bottom pan is plenty sufficient.

Re: 99 seville 100% tranny life since day one

The Eldorado readouts do not mention anything about the tranny fluid life. I think it is a '98 and up Seville option.

I never saw the purpose of changing the tranny fluid even at 100,000 miles. A neighbor of mine who owns a Gabralter transmission shop even said that it's not necessary for many transmissions - mainly GM transmissions. On the other hand he mentioned that Ford transmissions are completely different and that they require more attention.

Re: 99 seville 100% tranny life since day one

Hmm, why would a rental have less life left?? Have you ever seen someone driving the "rental". That about says it all.

The fact that the Deville is a rental, standing alone, cannot explain the discrepancy my friend.

First, this particular Deville had less than 9K on the clock. It is a rental used by the dealer and it is driven mostly by blue-haired old ladies. No way they are going to engage in brutal, constant, WOT driving. No way.

Second, a lot of the Sevilles that show 100% tranny fluid life after 30k, 50K, 60 or 70K miles on the clock HAVE been driven hard, or on stop and go situation where you would expect the computer to start counting down.

I think that there is something particular to the Seville tranny fluid life computer that keeps the reading at 100% life, even after extended, harsh driving.

Neither my dealer, nor anyone here, has been able to give me a completely satisfactory answer.

Maybe some of the forum members who have same-year Devilles can chime in here with their experience.

Personally, I am not too concerned. I will just follow the manual's recommendations and have the fluid changed at 100k miles.

But the fact that the Devilles were rentals is not a satisfactory answer.

Re: 99 seville 100% tranny life since day one

Originally Posted by 1toycad

The fact that the Deville is a rental, standing alone, cannot explain the discrepancy my friend.

First, this particular Deville had less than 9K on the clock. It is a rental used by the dealer and it is driven mostly by blue-haired old ladies. No way they are going to engage in brutal, constant, WOT driving. No way.

Second, a lot of the Sevilles that show 100% tranny fluid life after 30k, 50K, 60 or 70K miles on the clock HAVE been driven hard, or on stop and go situation where you would expect the computer to start counting down.

I think that there is something particular to the Seville tranny fluid life computer that keeps the reading at 100% life, even after extended, harsh driving.

Neither my dealer, nor anyone here, has been able to give me a completely satisfactory answer.

Maybe some of the forum members who have same-year Devilles can chime in here with their experience.

Personally, I am not too concerned. I will just follow the manual's recommendations and have the fluid changed at 100k miles.

But the fact that the Devilles were rentals is not a satisfactory answer.

I agree!
With only 9K miles on the clock, and if it was dogged half of those, the indicator should be at 100%. It is far less likely the car was dogged at all. Rental is not conclusive evidence of anything, other than more than one driver. A single algorithm error is far less likely than a fault. The most likely of all scenarios is that the mileage was incurred quickly from the time it was put into service, meaning that the accumulated mileage from zero to 9K was faster than normal. The computer does not keep track of time with just a clock or calendar, but it does count "run" cycles. A run cycle is start/run/cool-down. If the span of run cycles and miles do not match what is in the "normal" algorithm table, then the % will count down. The possibility is therefore conceivable one car may expire the predetermined life span early, while another is still at 100% at over 100K miles. Thus defining, the importance to follow the manufacturers' recommendation for fluid changes.